The invention relates to an apparatus for carrying out a weight measurement in centrifuges for separating suspensions into their solid and liquid components, comprising a machine housing, a drum rotatingly mounted in the machine housing and receiving the suspension, and a filler pipe leading into the drum for feeding the suspension into the drum, the machine housing being mounted for pivotal movement about an axis of rotation, and a force measuring element sensing weight-dependent deflections of the machine housing occurring about the axis of rotation and originating from a different degree of filling of the drum with suspension or from a different dewatering of the solid suspension components, and the machine housing deflections being indicated on a measurement value indicator.
An apparatus of this kind is known from DE 43 16 081 C1. In the front part of the housing a slight positive pressure can be generated in order to prevent separated liquid from passing over into the solids space. A slight negative pressure can be generated in the front part of the housing in order to prevent solids from passing over into the liquid discharge area when these are being withdrawn. It is, furthermore, known (WO 89/05193 A1; WO 92/04982 A1) to subject the drum of the centrifuge to positive pressure or negative pressure in order to, for example, influence the filtration process or the drying of the solid suspension components which are present in the form of a filter cake. However, on introducing a positive pressure or a negative pressure into the drum, interfering forces naturally occur which falsify the weight measurement of the centrifuge operating insofar like a beam-type balance.
The object of the invention is to so improve a generic apparatus that also upon introduction of a positive pressure or a negative pressure into the drum, no interference occurs in the weight-dependent measurements at the centrifuge.
The object is accomplished in accordance with claim 1 in a generic apparatus in that a pipeline is provided for generating a positive pressure or a negative pressure in the drum, and the line of application of the force generated in this pipeline on account of the positive pressure or the negative pressure is guided so as to intersect the axis of rotation of the machine housing.
In accordance with an embodiment of the invention, the object is accomplished in a generic apparatus in that a pipeline is provided for generating a positive pressure or a negative pressure in the drum, and a sensor sensing the pressure in the drum corrects the measurement value indicator in dependence upon the pressure.